1. Field
Integrated circuit processing.
2. Description of Related Art
Modern integrated circuits use conductive interconnections to connect the individual devices on a chip or to send and/or receive signals external to the device(s). Common types of interconnections include copper and copper alloy interconnections (lines) coupled to individual devices, including other interconnections (lines) by interconnections through vias.
A typical method of forming an interconnection, particularly a copper interconnection, is a damascene process. A typical damascene process involves forming a via and an overlying trench in a dielectric to an underlying circuit device, such as a transistor or an interconnection. The via and trench are then lined with a barrier layer of a refractory material, such as titanium nitride (TiN), tungsten nitride (WN), tantalum (Ta), or tantalum nitride (TaN). The barrier layer serves, in one aspect, to inhibit the diffusion of the interconnection material that will subsequently be introduced in the via and trench into the dielectric. Next, an adhesion layer may be formed on the barrier layer to improve the adhesion of a subsequently formed conductive interconnection to the barrier layer or the via and/or trench. Suitable materials for an adhesion layer include titanium (Ti), tantalum (Ta) and ruthenium (Ru). Next, a suitable seed material is deposited on the wall or walls of the via and trench. Suitable seed materials for the deposition of copper interconnection material include copper (Cu), nickel (Ni), cobalt (Co), and ruthenium (Ru). Next, interconnection material, such as copper, is introduced by electroplating or physical deposition in a sufficient amount to fill the via and trench and complete the interconnect structure. Once introduced, the interconnection structure may be planarized and a dielectric material (including an interlayer dielectric material) introduced over the interconnection structure to suitably isolate the structure.
Barrier layer and adhesion layer formation may be conducted by physical vapor deposition (PVD). In a PVD process, a surface of a substrate may be activated using temperature or a plasma which can degrade the surface. As via and trench widths become smaller, the conductivity and fill ability of an interconnection may be changed. For example, PVD deposition of a barrier layer into a narrow via or trench is typically not conformal (e.g. uniform thickness of the via or trench). In addition, an overhang of the PVD-deposited material at an opening of the via or trench may pinch-off the via or trench and inhibit the ability to fill the via or trench with conductive material.
Barrier layer and adhesion layer formation may also be formed by chemical vapor deposition (CVD) or atomic layer deposition (ALD). Such deposition processes also generally use increased temperature and/or plasma to drive off undesired ligands (ALD) or to activate a surface which can damage the substrate. In the case of CVD, conformality of a deposited film can be less than optimal.